Looking for His glorious appearing! Titus 2:13

For Colleen Simon, of Kansas City, Missouri, there's something about the month of May that brings dramatic change.

In May 2012, she wed the love of her life, Donna, in Iowa. It was also at that time she learned her cancer was in remission. The following May, she applied for – and later accepted – her dream job, a position that entailed running a food pantry at St Francis Xavier, a Roman Catholic church.

And this year, on 9 May, Simon was asked to resign from that job after her marriage to a local Lutheran reverend, Donna Simon, was noted in a magazine article.

"The reason for your involuntary separation of employment was based upon on irreconcilable conflict between the laws, discipline, and teaching of the Catholic Church and your relationship – formalized by an act of marriage in Iowa – to a person of the same sex," the Diocese of Kansas City-St Joseph said in its letter of dismissal.

Simon is only the latest addition to a growing list of gay employees fired in recent years by Catholic institutions for marrying, announcing plans to wed, or in some way making public their sexual orientation. This slate of terminations comes at a time when the Vatican led by Pope Francis is urging a softer tone toward gays and lesbians.

"I trusted the diocese on the promise they made to me, and the assurance that they made to me was broken: that my marriage would not affect my employment," Simon told the Guardian. "I'm deeply saddened that they did not follow through with that and chose to let me go."

Neither Missouri law nor federal law prohibit employers from hiring or firing people on the basis of their sexual orientation.

On Thursday, Simon and her lawyer filed a lawsuit against the Catholic Diocese of Kansas City-St Joseph and its Bishop, Robert Finn, alleging that she was wrongfully fired from her job at St Francis Xavier on the grounds that she had made clear to her employers before accepting the job that she was openly gay, and was assured that would not put her job in jeopardy.

The Church said in a statement on Thursday: "The Diocese has not seen the filing, so we cannot comment specifically at this time. In general, as a church we have the right to live and operate according to our faith and Church teachings. We regret this situation has resulted in litigation, however it is our sincere hope that the matter can be resolved amicably. As needed, we will defend our constitutional freedom to practice our faith and uphold the integrity of our mission and public witness."

'You could say the church brought us together'

Several years ago, Simon, who describes herself as deeply religious and very passionate about social justice, met her now-wife Donna while attending community organizing training.

"You could say the church brought us together," said Simon, a mother of two. After training, they stayed in touch, and eventually Simon moved to Kansas City "for love", she said. On 19 May, 2012, Simon and Donna married in Council Bluffs, Iowa, where same-sex marriage is legal.

“We wanted to be married legally in the eyes of the state and in God's church, to be married in the love of God as well,” Simon explained. Missouri's constitution prohibits same-sex marriage.

About a year later, Simon saw an opening at St Francis Xavier for what she still calls her "dream job". Well-aware of the tricky relationship some churches have with gay employees, Simon said she asked before applying if they would consider her for the position. She said she was encouraged to apply, and that she was honest and open about her sexual orientation throughout the hiring process.

During an interview, she said the pastor told her that there was no need to worry – and reassured her that what happened to a gay teacher at a Jesuit school in another state could not happen to her.

Simon, comforted by the pastor's words, accepted the job offer, she said.

In April, Simon and her wife Donna were both featured in a story published in the Kansas City Star’s 816 magazine about increasing diversity along Troost Avenue, a corridor “long-considered the city's racial dividing line”, the article said.

Simon and Donna, a reverend at St Mark Hope and Peace Lutheran church, which welcomes LGBT people and even flies a rainbow flag, said they had no idea the magazine story would cause a problem as they were both very open about their relationship. Donna quipped that kids at her church call Simon the “First Lady”.

But apparently the story had landed on the Bishop's desk and was indeed causing problems, Simon said.

After the article came out, Father Rafael Garcia, a new pastor at St Francis Xavier, called Kimberly Stern, a Kansas City-based freelance writer who wrote the story.

Stern, who is not involved in the case, confirmed that she received a call from Garcia after her article was published.

Stern said Garcia wanted to know what Simon told the reporter about her marriage to Donna and her sexuality. Then the pastor asked Stern if she was Catholic. When she responded that she was not, Stern said Garcia told her: "You have no idea what you've done."

'You're allowed to get married ... but not to keep your job'

On 9 May, Simon said she was called into Garcia's office, having no idea what she was about to walk into. She brought notes with her to the meeting, thinking they were going to discuss the church's upcoming events.

When she sat down in Garcia's office, she said she noticed that he was holding a piece of paper with the Diocese's letterhead, and her heart dropped.

Simon said Garcia told her that because her same-sex marriage was made public, he was forced to ask her to submit a letter of resignation.

Simon said she refused to resign as she believes she did nothing wrong, and was fired the following week.

She doesn't qualify for unemployment benefits because the diocese, as a religious employer, does not pay into the system.

Simon said she asked for her job back, but her request was not met. Supporters started an online petition calling on the diocese to reinstate Simon that collected more than 20,000 signatures, but nothing came of it. And in June, the parish announced they'd found a replacement for her job , according to the lawsuit.

After this, Simon said it was time to "ask with a different voice" and decided to file a lawsuit charging "fraudulent inducement" against the diocese and Bishop Finn, who she alleges compelled the church to fire her. She is seeking reinstatement, lost wages and damages.

Finn has been at the center of controversy previously, in 2012, when he became the first bishop in the US to be convicted for failing to report a suspected paedophile priest.

Simon, who was a practicing Catholic for many years before becoming Lutheran, said the experience has not shaken her faith, and believes the church simply needs time to evolve. She pointed out that in past decades, it wasn't unheard of for the church to fire employees who divorced or remarried.

Tony Rothert, the ACLU of Missouri's legal director, said cases like Simon's highlight the need for workplace protections for gay and lesbian people, especially as same-sex marriage makes gains in states across the US.

"There's going to be this dichotomy in the law that you're allowed to get married without discrimination but you're not allowed to keep your job,” he said.

A bill stalled in Congress would broadly extend workplace protections to all US employees, prohibiting employers from discriminating against people on the basis of sexual orientation and gender identity. But American civil rights and liberties groups, including the ACLU, recently dropped their support for the bill because of a provision that carves out exemptions for religious organizations.

In the meantime, Simon said she is praying she will be allowed to return to her job.

"I loved the job I was doing,” Simon said. “I loved the people I worked with and the people I worked for. I can forgive. I can forgive and move on. This is the work God called me to do.”